Single photon emission computerized tomography (SPECT) will be used to evaluate binding of 123I FP-CIT to dopamine transporters. This exam will allow calculation of the ratio of specific to non specific binding of 123I FP-CIT to dopamine transporters.

Pain perception will be evaluated by the determination of subjective pain thresholds (thermal pain thresholds, thermotest). A thermode will be used to determine the heat and cold pain thresholds.

Severity of Parkinson's disease will be evaluated with the Unified Parkinson's disease Rating Scale (UPDRS) and the Hoehn and Yahr scale

The mean rates of change and the variability around the mean of clinical, imaging and biomic outcomes in early PD patients, and the comparison of these rates between PD patient subsets and between PD, SWEDD, Prodromal and healthy subjects.

Comparison between the rates of change in the mean of clinical, imaging and biomic outcomes in early PD patients and between PD and healthy subjects

Prevalence of measures of clinical, imaging and biomic outcomes in early PD patients and healthy subjects.

Tracer uptake will be evaluated in regions of interest for analysis of regional [18F]MNI-958 binding/uptake and expressed in SUV by using established methods for normalization for 3 AD, 3 PSP, and 3 HV subjects.

To estimate the mean rates of change and the variability around the mean of clinical outcomes in PD patients over 3-5 years of follow-up comparing these rates between PD patients of each stage of the Hoehn and Yahr.

To determine the predictive value of iTUG/iSWAY test results on future course of the disease